Question

Two chambers, $A$ and $B$, containing solutions are separated by a semipermeable membrane.
$\left(a\right)$ Solution of which chamber has a lower water potential?
$\left(b\right)$ Solution of which chamber has a lower solute potential?
$\left(c\right)$ In which direction will osmosis occur?
$\left(d\right)$ Which solution has a higher solute potential?
$\left(e\right)$ At equilibrium which chamber will have lower water potential?
$\left(f\right)$ If one chamber has a $\Psi$ of $2000kPa$, and the other $1000kPa$, which is the chamber that has the higher $\Psi$?
$\left(g\right)$ What will be the direction of the movement of water when two solutions with ${\Psi }_w=0.2MPa$ and ${\Psi }_w=0.1MPa$ are separated by a selectively permeable membrane?

Answer 1

Water potential :
Water potential is denoted as $\Psi$, it is the difference between the potential energy/ free energy of pure water and a given water sample.

Final answer :
There is more solute in chamber $B$ as compared to chamber $A$, thus chamber $B$ will have lesser free water molecules and therefore lower water potential in comparison to chamber $A$.


Solute potential:
Solute potential is defined as the decrease in the water potential with the addition of solutes into it.
The water potential of pure water is 0 at standard conditions of temperature and pressure. As the number of solute molecules increases, the reduction in water potential is more. Thus the solute potential becomes more negative and the value decreases.


Final answer:
As the number of solute molecules increases, the solute potential decreases. Hence, chamber $B$ has a lower solute potential as because it has more solute molecules than chamber $A$.


Osmosis:
Osmosis is defined as a process where a solvent (for example, water) moves from a region of its higher concentration to lower concentration across a semipermeable membrane.

Final answer:
Chamber $A$ has more solvent and less solute than chamber $B$ and thus the direction of osmosis will be from chamber $A$ to chamber $B$.


Solute potential :
Solute potential is defined as the decrease in the water potential with the addition of solutes into it

Final answer :
The water potential of pure water is $0$ at standard conditions of temperature and pressure. As the number of solute molecules increases, the drop in magnitude of water potential is more and hence, solute potential decreases. If a solution has less number of solute molecules, its solute potential will be less negative and thus higher than that of a solution with higher solute concentration. Since, chamber $A$ has lesser solute molecules, thus it will have more solute potential than chamber $B$.


Water potential and equilibrium :
Water potential, denoted by $\Psi$ , is the difference between the potential energy of pure water and a given water sample. Equilibrium is a balanced condition when the free energy of both the systems are the same, resulting in a stable state.


Final answer :
Osmosis continues untill the difference in the water potential among two systems is retained. At equilibrium (balanced condition), the water potential is the same in both the chambers.


Water potential :
Water potential, denoted as Ѱ, is the difference between the potential energy/ free energy of pure water and a given water sample.

Final answer :
At standard temperature and pressure, the water potential of pure water is zero by convention. Thus more negative value denotes less water potential. So $-1000kPa$ will be considered to have higher water potential.


Selectively permeable membrane:
Selectively permeable membrane is the one which allows only particular types of solute molecules (solute with a specific size) to pass through it. It facilitates movement of selected solutes and solvent.


Final answer :
In the presence of a selectively permeable membrane, the movement of water is from higher water potential to lower water potential. Thus water will move from the solution having 0.2 MPa water potential to a solution having 0.1 MPa water potential.
Since a selectively permeable membrane might allow the solute to pass through, hence, reaching equilibrium will be comparatively complex.